1. Field of the Invention:
The invention relates to bit holders and base members for affixing the bit holder to the driven element of a mining machine or the like, and more particularly to bit holders and base members whereby the bit holders may be easily and quickly installed or removed and replaced.
2. Description of the Prior Art:
While the base member of the present invention may be applied to equipment other than mining machines, such as digging machines earthworking machines and the like, for purposes of an exemplary showing it will be described with respect to its use on mining machines.
It has long been recognized that mining cutter bits wear out fast and need frequent replacement. In recent years it has also been recognized that the cutter bit holders wear out quicker than the base members and that it would be desirable to provide means for the ready replacement of such holders. Prior art workers attempted to accomplish this by various types of "pin-on" arrangements. An early example of this is disclosed in U.S. Pat. No. 3,338,634. The pins of these arrangements, however, bore substantially all of the resultant cutting forces and were subject to wear and failure. This problem was solved by the invention disclosed in U.S. Pat. No. Re. 28,310 wherein the bit holder and base member, although joined by a connecting pin, were also provided with cooperating abutment surfaces which sustained a good portion of the resultant cutting forces encountered during mining operations. In most of the arrangements of the last mentioned patent, however, the connecting pin extended laterally beyond the edges of the joined bit holder and base member, and the retaining means for such connecting pin were also located beyond the sides of the joined members. Such arrangement required more space and created interference during mining operations.
The present invention eliminates the need for either the connecting pin or its retaining means to be laterally offset from the joined bit holder and base member.
The invention is particularly well suited for use with bit holders and base members of the type shown in FIGS. 1 through 10 of U.S. Pat. No. Re. 28,310 and various of the arrangements depicted in U.S. Pat. No. 3,397,012; for bit holders and base members of the type shown in FIGS. 11 and 14 of U.S. Pat. No. Re. 28,310 and U.S. Pat. No. 3,519,309; for the bit holder and base member of FIG. 12 of U.S. Pat. No. Re. 28,310 and the combinations possible stemming from the combined teachings of U.S. Pat. Nos. 3,397,012 and 3,519,309; and for the bit holder and base member of FIG. 13 of U.S. Pat. No. Re. 28,310 and for various of the arrangements of U.S. Pat. No. 2,965,365.
It should also be noted, however, that the foregoing patents are mentioned only as being exemplary of the art to which the instant invention may be applied. Other prior art patents disclosing additional bit systems to which this invention may be applied are U.S. Pat. Nos. 3,622,206 and 3,841,703.
Furthermore, there is additional prior art which may be pertinent to certain forms of this invention. Attention is called, for example, to the following group of U.S. Pat. Nos. 2,623,398; 2,766,979; 2,802,368 and 2,802,369. Other pertinent U.S. Pats. are Nos. 2,741,139 and No. 2,826,085. These latter patents disclose other combinations in which D-shaped members have been employed, although not in the various combinations of bit holders and base members to which this invention is directed.